Yeast is a microorganism, a type of fungus, that plays a crucial role in the fermentation process, where it converts sugars into alcohol and carbon dioxide. The most common type used in baking and brewing is Saccharomyces cerevisiae. Yeast is created through a process of fermentation, which can occur naturally or be cultivated in controlled environments. In dry form, yeast is typically produced by drying live yeast cells, which are then inactive until rehydrated with water. Dry yeast was first introduced in the late 19th century as a more convenient and longer-lasting alternative to fresh yeast. This innovation revolutionized the baking industry, allowing bakers to store yeast for longer periods and providing more consistent results in bread and other baked goods. The development of dry yeast greatly impacted food production, making home baking more accessible and improving the consistency of bread, beer, and other fermented products.